An X-ray diagnostic apparatus irradiates a subject with X-rays, and based on the transmitted X-rays, generates an X-ray image representing differences in attenuation of the X-rays in a subject with black-and-white density. Such an X-ray image is displayed on various types of displays, and is viewed when, for example, a contrast radiography examination, such as an angiography, or an interventional treatment is performed. The black-and-white gradation in the X-ray image generated by the X-ray diagnostic apparatus is converted into a gradation expressed by a display when displayed on the display.